Color diffusion transfer processes generally involve the use of a photographic element comprising a support, at least one silver halide emulsion and an image dye-providing material which is contained in or contiguous said layer. After exposure, such a photographic element is treated with an alkaline processing solution to effect imagewise discrimination in the element. As is well known in the art, the dye-providing material can be initially immobile or initially mobile in the processing solution. Upon alkaline processing of an initially immobile dye-providing material, a mobile dye or dye precursor can be released imagewise or the material can be imagewise rendered soluble and thus mobile. If the material is initially mobile, the processing solution typically renders the material insoluble (and thus immobile) in an imagewise fashion. Whether initially mobile or immobile, upon treatment with a processing solution, the dye-providing material typically is oxidized under alkaline conditions thereby producing imagewise discrimination in the element.
Exemplary of such color diffusion transfer processes are those using developing agents as disclosed in U.S. Pat. Nos. 2,698,798 and 2,559,643 wherein a latent silver halide image is developed with a color developing agent. As development proceeds, the color developing agent reduces the exposed silver halide to metallic silver and the color developing agent which is oxidized as a function of development forms an immobile species while the unoxidized color developing agent is free to migrate to a receiving element. After migration, the color developing agent in the receiver is oxidized. The oxidized developing agent then self-couples or couples with a color coupler to form a positive dye image.
A more recent example of a photographic process in which oxidation causes formation of an image dye is described in copending Lestina and Bush U.S. application Ser. No. 308,869, filed Nov. 22, 1972, now U.S. Pat. No. 3,880,058, and entitled PHOTOGRAPHIC ELEMENTS CONTAINING OXICHROMIC COMPOUNDS. Those oxichromic compounds are ones which undergo chromogenic oxidation to form a new chromophore. Useful materials of that type are oxichromic compounds which contain a developing moiety and an oxichromic moiety and have the general formula D-(OC) wherein D is a group which is a silver halide developer such as hydroquinone moiety and OC is a moiety which undergoes chromogenic oxidation to form an image dye. These oxichromic compounds are particularly useful in an image transfer unit format in which the respective initially diffusible oxichromic compounds or the initially nondiffusible compounds are used in combination with the appropriate silver halide emulsions.
In order to achieve optimum results when using such oxichromic compounds, it is desirable to have an oxidant which can be easily incorporated in a photographic element with good stability and which will readily oxidize the oxichromic moiety without adversely affecting other ingredients of a given photographic element or film unit. The oxidative conversion of oxichromic compounds or of other color-providing materials is necessary in order to achieve color image formation. Accordingly, there is a continuing need in the art for materials which exhibit suitable oxidation capability.